Microbial Ecology and Evolution
I .- The ecology and evolution of multicellularity.
This project is motivated by the life cycle of Dictyostelium discoideum, which combines a unicellular and a multicellular phase. Upon starvation, part of the cells aggregate to form a fruiting body made of dead stalk cells and reproductive spores. Amoebae do not discriminate genetic non-relatives during aggregation, so they can form genetically heterogeneous fruiting bodies. This makes the persistence of the cooperative multicellular phase challenging to explain. Previous theoretical studies appeal to game theoretical approaches, but they undermine the role of the ecological context and use a one dimensional fitness set only by the number of spores. This picture is incomplete, and can lead to paradoxical results. In this project, together with Corina E. Tarnita (Princeton University), we propose the construction of a theoretical framework that includes ecological factors, such as fluctuations in the resources, and tradeoffs between multiple fitness components, as represented by spore number versus spore viability, to test whether multicellularity emerges as a survival strategy in unpredictable environments and how cooperation within multicellular organisms prevails in the face of defectors. This theoretical part is combined with experimenal work, done by Fernando Rossine (Princeton University), which will not only confirm theoretical predictions provided by well-mixed and individual based models, but also open new directions of research. Other collaborators are Tomas Gregor (Princeton University), Allyson E. Sgro (Boston University), Simon A. Levin (Princeton University) and Alex Washburne (Duke University).
This project is motivated by the life cycle of Dictyostelium discoideum, which combines a unicellular and a multicellular phase. Upon starvation, part of the cells aggregate to form a fruiting body made of dead stalk cells and reproductive spores. Amoebae do not discriminate genetic non-relatives during aggregation, so they can form genetically heterogeneous fruiting bodies. This makes the persistence of the cooperative multicellular phase challenging to explain. Previous theoretical studies appeal to game theoretical approaches, but they undermine the role of the ecological context and use a one dimensional fitness set only by the number of spores. This picture is incomplete, and can lead to paradoxical results. In this project, together with Corina E. Tarnita (Princeton University), we propose the construction of a theoretical framework that includes ecological factors, such as fluctuations in the resources, and tradeoffs between multiple fitness components, as represented by spore number versus spore viability, to test whether multicellularity emerges as a survival strategy in unpredictable environments and how cooperation within multicellular organisms prevails in the face of defectors. This theoretical part is combined with experimenal work, done by Fernando Rossine (Princeton University), which will not only confirm theoretical predictions provided by well-mixed and individual based models, but also open new directions of research. Other collaborators are Tomas Gregor (Princeton University), Allyson E. Sgro (Boston University), Simon A. Levin (Princeton University) and Alex Washburne (Duke University).
II .- Bacterial spatio-temporal patterns.
Biofilms are bacterial conglomerates usually formed attached to surfaces. Among many other features, bacteria within a biofilm enhance their virulence and resistance to antibiotics. Together with Juan A. Bonachela (Strathclyde University) and Carey Nadell (Dartmouth College), we are using physics toy models and microfluidic experiments with V. cholerae to understand the ecological and evolutionary implications of the biofilm matrix (which allow cells to stick together) during the colonization of different environments. To that end, we set up experiments using two identical strains of V. Cholerae, genetically modified to allow or suppress the expression of the genes that control the formation of the matrix. We modify the initial conditions of the surface colonization, and try to replicate the observed final occupation patterns with simple cellular automaton models. Our models allow us to vary the ecological conditions as well as to play with the degree of stickiness of the cells and explore a much broader range of scenarios. Other collaborators in this project are: Knut Drescher and Raimo Hartmann (Max Planck Institute in Terrestial Microbiology).
Biofilms are bacterial conglomerates usually formed attached to surfaces. Among many other features, bacteria within a biofilm enhance their virulence and resistance to antibiotics. Together with Juan A. Bonachela (Strathclyde University) and Carey Nadell (Dartmouth College), we are using physics toy models and microfluidic experiments with V. cholerae to understand the ecological and evolutionary implications of the biofilm matrix (which allow cells to stick together) during the colonization of different environments. To that end, we set up experiments using two identical strains of V. Cholerae, genetically modified to allow or suppress the expression of the genes that control the formation of the matrix. We modify the initial conditions of the surface colonization, and try to replicate the observed final occupation patterns with simple cellular automaton models. Our models allow us to vary the ecological conditions as well as to play with the degree of stickiness of the cells and explore a much broader range of scenarios. Other collaborators in this project are: Knut Drescher and Raimo Hartmann (Max Planck Institute in Terrestial Microbiology).
